Human brain bigger than chimp’s from foetal stage

Human brain is larger than that of their chimp cousins from the foetal stage itself, says the first ever study to track and compare their brain growths.

Satoshi Hirata of Kyoto University and colleagues Tomoko Sakai and Hideko Takeshita have found that human and chimp brains begin to show remarkable differences very early in life.

The image shows a 3D ultrasound of a chimp in the womb.

“Nobody knew how early these differences between human and chimp brains emerged,” said Hirata. In both primate species, the brain grows increasingly fast in the womb initially, the journal Current Biology reports.

After 22 weeks of gestation, brain growth in chimps starts to level off, while that of humans continues to accelerate for another two months or more. (Human gestation time is 38 weeks compared to chimps’ 33 or 34 weeks), according to Kyoto University.

The findings are based on 3D ultrasound imaging of pregnant chimps from 14 to 34 weeks of gestation and comparison of those foetal images to those of human foetuses.

While early brain differences were suspected, no one had previously measured the volume of chimpanzee brains as they develop in the womb, until now. The findings are part of a larger effort by the research team to explore differences in primate brains.

In another Current Biology report published last year, they compared brain development in chimps versus humans via magnetic resonance imaging (MRI) scans of growing chimpanzees from the age of six months to six years.

“Elucidating these differences in the developmental patterns of brain structure between humans and great apes will provide important clues to understand the remarkable enlargement of the modern human brain and humans’ sophisticated behaviour,” Sakai said.